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Question 1WLAN RF Fundamentals and Propagation

A transmitter's output power is doubled. How much does the power level increase in decibels?

  1. 10 dB
  2. 3 dB Correct answer.
  3. 1 dB
  4. 6 dB

Explanation

A doubling of power corresponds to a 3 dB increase, because 10 x log10(2) is approximately 3. Doubling again (4x) would add another 3 dB, for 6 dB total. The 10 dB step corresponds to a tenfold change in power, not a doubling.

Question 2WLAN RF Fundamentals and Propagation

A radio output of 10 mW is equivalent to which power level?

  1. 0 dBm
  2. 30 dBm
  3. 20 dBm
  4. 10 dBm Correct answer.

Explanation

dBm is referenced to 1 mW, so a value in mW is converted with 10 x log10(mW). Since log10(10) equals 1, 10 mW is 10 dBm. The 0 dBm reference point is exactly 1 mW.

Question 3WLAN RF Fundamentals and Propagation

What is the approximate free-space wavelength of a 2.4 GHz signal?

  1. 1.25 cm
  2. 12.5 cm Correct answer.
  3. 30 cm
  4. 3.3 cm

Explanation

Wavelength equals the speed of light divided by frequency, so 3 x 10^8 m/s divided by 2.4 x 10^9 Hz gives about 0.125 m, or 12.5 cm. Higher frequencies produce shorter wavelengths and lower frequencies produce longer ones.

Question 4WLAN RF Fundamentals and Propagation

Which of the following frequencies has the shortest wavelength?

  1. 900 MHz
  2. 2.4 GHz
  3. 5 GHz
  4. 6 GHz Correct answer.

Explanation

Wavelength is inversely proportional to frequency, so the highest frequency has the shortest wavelength. Among the choices, 6 GHz is the highest frequency and therefore produces the shortest wave.

Question 5WLAN RF Fundamentals and Propagation

How is EIRP calculated from a transmitter's settings?

  1. Transmit power minus gain, minus cable loss
  2. Transmit power plus gain, plus cable loss
  3. Transmit power minus gain, plus cable loss
  4. Transmit power plus gain, minus cable loss Correct answer.

Explanation

EIRP is the effective power radiated from an isotropic reference and equals transmit power plus antenna gain, with any cabling and connector losses subtracted. Gain from the antenna increases the radiated level while loss in the feed line reduces it.

Question 6WLAN RF Fundamentals and Propagation

At a fixed distance, how does free-space path loss behave as frequency increases?

  1. Path loss increases as frequency increases Correct answer.
  2. Path loss decreases as frequency increases
  3. Path loss increases as frequency decreases
  4. Path loss depends only on distance

Explanation

Free-space path loss grows with both distance and frequency, since the formula includes a 20 log of each term. This is why higher bands such as 5 GHz and 6 GHz attenuate more quickly than 2.4 GHz over the same span.

Question 7WLAN RF Fundamentals and Propagation

What first Fresnel zone clearance is generally recommended for a reliable point-to-point link?

  1. 100%
  2. 40%
  3. 20%
  4. 60% Correct answer.

Explanation

A clearance of roughly 60% of the first Fresnel zone radius is the standard design goal for line-of-sight links. This keeps diffraction losses from terrain, rooftops, or other obstructions small. Full 100% clearance is rarely achievable and is not required.

Question 8WLAN RF Fundamentals and Propagation

What does RSSI represent on a WLAN client device?

  1. A calibrated power reading in dBm
  2. A vendor-scaled strength indicator Correct answer.
  3. A signal-to-noise ratio value
  4. A maximum supported data rate

Explanation

RSSI is a relative index that each chipset vendor scales in its own way, so values from different vendors are not directly comparable. It is not a calibrated power measurement; true signal level is usually reported separately in dBm.

Question 9WLAN RF Fundamentals and Propagation

An access point transmits at 20 dBm. After adding a 3 dB increase, what is the new power level?

  1. 400 mW
  2. 40 mW
  3. 200 mW Correct answer.
  4. 100 mW

Explanation

First convert to linear power: 20 dBm is 100 mW, and a 3 dB increase doubles power, giving 200 mW, which equals 23 dBm. Working in dB is simpler: 20 dBm plus 3 dB is 23 dBm.

Question 10WLAN RF Fundamentals and Propagation

What is the free-space path loss for a 2.4 GHz link spanning 100 meters?

  1. 80 dB Correct answer.
  2. 68 dB
  3. 92 dB
  4. 100 dB

Explanation

Using FSPL in dB equals 32.44 plus 20 log(f in MHz) plus 20 log(d in km): 32.44 plus 67.6 minus 20 is about 80 dB. The distance term is negative because 100 m is 0.1 km.

Question 11WLAN RF Fundamentals and Propagation

Signal-to-noise ratio is calculated as which of the following?

  1. Received signal level minus noise floor Correct answer.
  2. Transmit power minus path loss
  3. Noise floor minus received signal level
  4. Received signal level plus noise floor

Explanation

SNR expresses how far the received signal sits above the background noise, so it is the received signal level minus the noise floor in dB. A larger difference means a cleaner signal and supports higher modulation rates.

Question 12WLAN RF Fundamentals and Propagation

Doubling a channel from 20 MHz to 40 MHz has what effect on the thermal noise floor?

  1. Leaves it unchanged
  2. Raises it by 3 dB Correct answer.
  3. Raises it by 6 dB
  4. Lowers it by 3 dB

Explanation

Thermal noise power is proportional to bandwidth, so each doubling of width adds about 3 dB of noise. A 40 MHz channel therefore collects twice the noise power of a 20 MHz channel. Wider channels gain throughput but lose SNR margin.

Question 13WLAN RF Fundamentals and Propagation

What is the primary consequence of multipath in a WLAN environment?

  1. Higher antenna gain at the receiver
  2. A lower thermal noise floor
  3. Narrower Fresnel zone requirements
  4. Intersymbol interference and signal fading Correct answer.

Explanation

Reflected copies of the signal arrive with different delays and phases, so they combine constructively or destructively at the receiver. The result is fading and intersymbol interference, which OFDM and MIMO techniques are designed to mitigate.

Question 14WLAN RF Fundamentals and Propagation

Which propagation mechanism describes an RF wave bending around the edge of an obstruction?

  1. Scattering
  2. Absorption
  3. Diffraction Correct answer.
  4. Refraction

Explanation

Diffraction occurs when a wave encounters an edge and its energy spreads into the shadowed region behind it, allowing partial coverage even without line of sight. It is why signals can reach behind rooftops and hilltops.

Question 15WLAN RF Fundamentals and Propagation

Which propagation mechanism converts RF energy into heat as it passes through a material?

  1. Diffraction
  2. Scattering
  3. Reflection
  4. Absorption Correct answer.

Explanation

Absorption takes energy out of the wave and dissipates it as heat within the material, which is why thick walls reduce signal level. Water-bearing materials such as foliage and concrete are especially absorptive at 2.4 GHz.

Question 16WLAN RF Fundamentals and Propagation

A vertically polarized access point serves a client whose antenna is horizontally polarized. What mismatch loss should be expected?

  1. +20 dB Correct answer.
  2. +3 dB
  3. +6 dB
  4. +0 dB

Explanation

Polarization mismatch follows a cosine relationship; at 90 degrees the theoretical loss is total, and in practice 20 dB or more is observed. Aligning transmit and receive polarization avoids this penalty.

Question 17WLAN RF Fundamentals and Propagation

An AP has an EIRP of 20 dBm. The path loss is 100 dB, the receiving antenna provides 5 dBi, and the receiver cable loses 2 dB. What is the received signal level?

  1. -73 dBm
  2. -77 dBm Correct answer.
  3. -67 dBm
  4. -83 dBm

Explanation

Start with the EIRP, subtract path loss, then add receive antenna gain and subtract receive cable loss: 20 minus 100 plus 5 minus 2 equals -77 dBm. Link budgets are simply a running sum of gains and losses in dB.

Question 18WLAN RF Fundamentals and Propagation

Where along a point-to-point path is the first Fresnel zone the widest?

  1. It is equal everywhere
  2. At the midpoint Correct answer.
  3. At the transmitter
  4. At the receiver

Explanation

The Fresnel zone radius depends on the distance from each end of the path and reaches its maximum at the midpoint. This is why the midpoint is where obstructions most often cause trouble.

Question 19WLAN RF Fundamentals and Propagation

Which mechanism produces the strong delayed copy of a signal received over a large flat reflective surface?

  1. Absorption
  2. Refraction
  3. Reflection Correct answer.
  4. Diffraction

Explanation

Smooth, large surfaces such as water, metal roofs, and glass reflect a substantial portion of the wave, producing a second signal with extra path delay. The delayed copy can combine destructively with the direct signal.

Question 20WLAN RF Fundamentals and Propagation

Two links use identical equipment and distances, one at 5 GHz and one at 6 GHz. How does the 6 GHz link compare?

  1. It has the same path loss
  2. It has greater path loss Correct answer.
  3. It has less path loss
  4. It has a wider Fresnel zone

Explanation

Because free-space path loss includes a 20 log of frequency, moving from 5 GHz to 6 GHz adds roughly 1.6 dB of loss at the same distance. Higher bands also penetrate obstacles less effectively.

Question 21WLAN RF Fundamentals and Propagation

A bridge link uses a 24 dBm radio, 2 dB of cable loss per end, 25 dBi antennas at both ends, and a 118 dB path loss. What is the received signal level?

  1. -52 dBm
  2. -58 dBm
  3. -44 dBm
  4. -48 dBm Correct answer.

Explanation

Build the budget end to end: 24 minus 2 plus 25 gives 47 dBm EIRP, then minus 118 dB of path loss, plus 25 dBi receive gain, minus 2 dB receive cable loss equals -48 dBm. Including both antenna gains and both cable losses is essential for a correct result.

Question 22WLAN RF Fundamentals and Propagation

A link's distance is doubled and its frequency is also doubled. How much additional path loss results?

  1. 12 dB Correct answer.
  2. 20 dB
  3. 6 dB
  4. 3 dB

Explanation

Each doubling contributes 6 dB of free-space path loss: 20 log(2) is about 6 dB for distance and another 6 dB for frequency. The two effects add, producing roughly 12 dB of extra loss.

Question 23WLAN RF Fundamentals and Propagation

Why is a 20 to 30 dB fade margin included in an outdoor non-line-of-sight link budget?

  1. To permit a higher transmit power setting
  2. To offset the effects of channel bonding
  3. To cover deep multipath fades below the average level Correct answer.
  4. To absorb antenna misalignment error

Explanation

Without a dominant direct path, the received envelope is statistically described by a Rayleigh distribution, whose nulls can drop tens of dB below the mean. The fade margin keeps the link above the sensitivity threshold during those dips.

Question 24WLAN RF Fundamentals and Propagation

A cable and antenna system has a return loss of 10 dB. What percentage of the incident power is reflected?

  1. 10% Correct answer.
  2. 25%
  3. 1%
  4. 50%

Explanation

Return loss in dB is 10 log of the incident-to-reflected power ratio, so a 10 dB value means reflected power is one-tenth of incident power. The remaining 90% enters the load. Lower return loss values indicate worse impedance matching.

Question 25WLAN RF Fundamentals and Propagation

What is the theoretical thermal noise floor in a 20 MHz wide channel at room temperature?

  1. -101 dBm Correct answer.
  2. -89 dBm
  3. -107 dBm
  4. -95 dBm

Explanation

Thermal noise density at room temperature is about -174 dBm per hertz; adding 10 log(20,000,000), or 73 dB, gives roughly -101 dBm. A real receiver adds its noise figure on top of this figure.

Question 26WLAN RF Fundamentals and Propagation

What power level in milliwatts corresponds to 0 dBm?

  1. 0 mW
  2. 10 mW
  3. 100 mW
  4. 1 mW Correct answer.

Explanation

0 dBm is the reference point for the dBm scale and is defined as 1 milliwatt. The conversion is P(dBm) = 10 log10(P(mW) / 1 mW).

Question 27WLAN RF Fundamentals and Propagation

Increasing an RF power level by 10 dB multiplies the power by what factor?

  1. 100
  2. 20
  3. 10 Correct answer.
  4. 2

Explanation

A 10 dB increase represents a tenfold increase in power because 10 log10(10) = 10 dB. A 3 dB increase is approximately a doubling of power.

Question 28WLAN RF Fundamentals and Propagation

An antenna gain of 6 dBd is equivalent to approximately what gain in dBi?

  1. 6 dBi
  2. 3.85 dBi
  3. 8.15 dBi Correct answer.
  4. 12 dBi

Explanation

The dBi scale references an isotropic radiator, while dBd references a half-wave dipole. A dipole has 2.15 dBi of gain, so dBi = dBd + 2.15.

Question 29WLAN RF Fundamentals and Propagation

What does effective isotropic radiated power (EIRP) represent?

  1. Power referenced to an isotropic radiator, including gain and feedline loss Correct answer.
  2. Conducted power measured at the radio connector before the antenna is attached
  3. The total electrical power consumed by the radio and the antenna system combined
  4. The minimum signal level that the receiver can detect above its noise floor

Explanation

EIRP is the equivalent power that would be radiated by an isotropic antenna to produce the same signal strength in the main direction. It is calculated from conducted transmit power plus antenna gain minus feedline and connector losses.

Question 30WLAN RF Fundamentals and Propagation

For antennas of similar design efficiency, what happens to antenna gain as the horizontal beamwidth narrows?

  1. Gain becomes circularly polarized
  2. Gain stays the same because beamwidth and gain are unrelated
  3. Gain increases as energy is concentrated into a smaller area Correct answer.
  4. Gain decreases because the beam covers less area

Explanation

For a given antenna efficiency, directivity and gain rise as the radiation pattern becomes narrower. Concentrating the same power into a smaller angular area increases the power density in that direction.

Question 31WLAN RF Fundamentals and Propagation

In a WLAN environment, a large delay spread between multipath components most directly leads to which impairment?

  1. Inter-symbol interference Correct answer.
  2. Increased antenna gain
  3. Lower cable loss
  4. Reduced thermal noise floor

Explanation

Delay spread is the time difference between the earliest and latest significant multipath arrivals. When the spread is large relative to the symbol period, delayed copies overlap later symbols and cause inter-symbol interference.

Question 32WLAN RF Fundamentals and Propagation

In an indoor office environment, which path-loss exponent is most typical compared with the free-space value of 2?

  1. 3 to 4 Correct answer.
  2. 0.5 to 1
  3. 2 exactly
  4. 1 to 1.5

Explanation

Indoor environments contain walls, furniture, and people that absorb, reflect, and scatter RF energy. This adds loss beyond free-space spreading, so the path-loss exponent is typically 3 to 4 rather than 2.

Question 33WLAN RF Fundamentals and Propagation

A receiver with sensitivity of -90 dBm receives a signal at -82 dBm. What is the link margin?

  1. 8 dB Correct answer.
  2. 10 dB
  3. 12 dB
  4. 6 dB

Explanation

Link margin is the difference between the received signal level and the receiver sensitivity. Here, -82 dBm minus -90 dBm equals 8 dB of margin.

Question 34WLAN RF Fundamentals and Propagation

How does SINR differ from SNR?

  1. It includes interference with noise in the denominator Correct answer.
  2. It is always expressed in linear milliwatts rather than decibels
  3. It completely ignores the thermal noise floor of the receiver
  4. It is measured only at the transmitter's output connector

Explanation

SNR compares signal power only with the noise floor, while SINR compares signal power with noise plus interference. SINR therefore reflects the effect of co-channel and adjacent-channel interference.

Question 35WLAN RF Fundamentals and Propagation

How does foliage attenuation generally change as the signal frequency increases from 2.4 GHz to 5 GHz?

  1. It decreases because shorter wavelengths pass through leaves more easily
  2. It remains identical at both frequencies
  3. It generally increases at the higher frequency Correct answer.
  4. It becomes zero above 5 GHz

Explanation

Vegetation loss generally increases with frequency because shorter wavelengths interact more strongly with leaves and branches. The effect is modest from 2.4 to 5 GHz but still tends to grow at the higher frequency.

Question 36WLAN RF Fundamentals and Propagation

Two access points in the same coverage area are configured on the same 20 MHz channel. What is the primary result?

  1. The APs automatically combine their throughput
  2. Co-channel interference degrades performance Correct answer.
  3. The clients switch to a different band automatically
  4. The channel's noise floor drops by 3 dB

Explanation

Access points on the same channel share airtime and their signals add as interference where coverage overlaps. This co-channel interference reduces throughput and can increase retransmissions.

Question 37WLAN RF Fundamentals and Propagation

If the delay spread in a channel increases, what happens to the coherence bandwidth?

  1. It increases proportionally
  2. It stays constant
  3. It decreases Correct answer.
  4. It becomes equal to the carrier frequency

Explanation

Coherence bandwidth is the range of frequencies over which the channel response is roughly flat. It is inversely proportional to delay spread, so greater delay spread produces a narrower coherence bandwidth.

Question 38WLAN RF Fundamentals and Propagation

Why might a link use circular polarization instead of linear polarization?

  1. It lowers the free-space path loss
  2. It eliminates the need for Fresnel zone clearance
  3. It tolerates antenna rotation misalignment Correct answer.
  4. It doubles the available transmit power

Explanation

Circular polarization rotates as the wave propagates, so a receiving antenna of the same sense maintains a usable signal even if its orientation changes. Linear polarization suffers additional mismatch loss when the antennas are rotated relative to each other.

Question 39WLAN RF Fundamentals and Propagation

For a mobile client moving at a fixed speed, how does the maximum Doppler shift change as the carrier frequency increases?

  1. It stays the same because speed is unchanged
  2. It depends only on the antenna gain
  3. It increases as the wavelength shortens Correct answer.
  4. It decreases because wavelength increases

Explanation

Doppler shift is proportional to velocity divided by wavelength. For a fixed speed, a higher carrier frequency means a shorter wavelength and therefore a larger maximum Doppler shift.

Question 40WLAN RF Fundamentals and Propagation

A point-to-point bridge was designed for full first Fresnel zone clearance, but a rooftop edge now intrudes so that only about 60 percent of the first Fresnel zone radius remains unobstructed. What is the most likely effect on the link?

  1. Roughly 20 dB of diffraction loss, rendering the link unusable
  2. Exactly 3 dB of loss, because half of the zone is blocked
  3. Little measurable loss, since 60 percent clearance is generally acceptable Correct answer.
  4. Complete loss of signal, because the path is no longer line-of-sight

Explanation

Practical link design requires that at least 60 percent of the first Fresnel zone radius be clear of obstructions; below that threshold diffraction loss grows quickly, while at or above it the loss is small. A path meeting the 60 percent criterion is still treated as effectively line-of-sight for RF purposes, even if a structure intrudes into the outer part of the zone.

Question 41WLAN Design and Site Survey

In the 2.4 GHz band as regulated in the United States, how many non-overlapping 20 MHz channels are available for a multi-AP deployment?

  1. 6
  2. 3 Correct answer.
  3. 14
  4. 11

Explanation

2.4 GHz channels are numbered in 5 MHz steps but each occupies roughly 20 MHz of spectrum, so only channels 1, 6, and 11 avoid spectral overlap in the FCC domain. The band contains 11 usable channels, but most of them overlap each other.

Question 42WLAN Design and Site Survey

Which type of site survey relies on a software model of the building and AP specifications to estimate coverage before any equipment is installed?

  1. Active survey
  2. Passive survey
  3. Predictive survey Correct answer.
  4. Validation survey

Explanation

A predictive (virtual) survey uses floor-plan attenuation values and vendor antenna patterns in a modeling tool to estimate coverage and AP count before hardware exists. Its results are later confirmed by on-site measurement.

Question 43WLAN Design and Site Survey

How is signal-to-noise ratio (SNR) determined at a given location?

  1. By adding the noise floor to the received signal level
  2. By measuring the strongest overlapping SSID at that location
  3. By dividing the received signal power by the transmit power
  4. By subtracting the noise floor in dBm from the received signal level in dBm Correct answer.

Explanation

Both received signal and noise floor are expressed as logarithmic power levels, so the ratio in dB is the arithmetic difference between them. For example, −65 dBm signal with a −95 dBm noise floor gives 30 dB SNR.

Question 44WLAN Design and Site Survey

Which antenna type provides roughly equal coverage in all horizontal directions and is typically mounted in the center of an open office?

  1. Parabolic grid
  2. Yagi
  3. Omnidirectional Correct answer.
  4. Patch

Explanation

An omnidirectional antenna radiates a donut-shaped pattern with approximately 360 degrees of azimuth coverage, which suits a centrally mounted AP serving an open area. Directional types concentrate energy into a narrower beam.

Question 45WLAN Design and Site Survey

Which expression correctly calculates EIRP for an AP with a 20 dBm radio, a 6 dBi antenna, and 2 dB of cable loss?

  1. 20 + 6 − 2 = 24 dBm Correct answer.
  2. 20 − 6 + 2 = 16 dBm
  3. 20 × 6 ÷ 2 = 60 dBm
  4. 20 + 6 + 2 = 28 dBm

Explanation

EIRP equals transmitter power plus antenna gain minus cable and connector losses, with all terms in dB or dBm. Here 20 dBm + 6 dBi − 2 dB = 24 dBm.

Question 46WLAN Design and Site Survey

A Wi-Fi adapter reports a healthy SNR, yet clients disconnect intermittently. Which tool best identifies a nearby microwave oven or cordless phone as the cause?

  1. Spectrum analyzer Correct answer.
  2. Predictive planning tool
  3. RADIUS server log
  4. Protocol analyzer capturing 802.11 frames

Explanation

A spectrum analyzer sweeps the RF band and displays energy from any source, including non-802.11 devices that a Wi-Fi adapter may filter or only report as elevated noise. This makes it the right tool for identifying interferers outside the 802.11 standards.

Question 47WLAN Design and Site Survey

For the same distance and antenna configuration, how does free-space path loss at 5 GHz compare with 2.4 GHz?

  1. It depends only on transmit power
  2. It is lower at 5 GHz
  3. It is higher at 5 GHz Correct answer.
  4. It is identical

Explanation

The free-space path loss formula includes a 20 log(f) term, so loss grows with frequency. At any given distance a 5 GHz signal is attenuated more than a 2.4 GHz signal, all else being equal.

Question 48WLAN Design and Site Survey

Which channel width yields the largest number of non-overlapping channels in the 5 GHz band for a high-density deployment?

  1. 40 MHz
  2. 80 MHz
  3. 20 MHz Correct answer.
  4. 160 MHz

Explanation

Wider channels consume more contiguous spectrum, so narrowing the channel increases the number of non-overlapping channels available for reuse. A 20 MHz plan maximizes the number of cells that can operate without overlapping each other.

Question 49WLAN Design and Site Survey

For a point-to-point bridge, what minimum clearance of the first Fresnel zone is generally recommended to avoid significant signal loss?

  1. 40 percent
  2. 100 percent
  3. 60 percent Correct answer.
  4. 20 percent

Explanation

Obstruction of the first Fresnel zone beyond about 40 percent begins to cause noticeable loss, so designs commonly specify at least 60 percent clearance. Full 100 percent clearance is not required for a workable link.

Question 50WLAN Design and Site Survey

An AP transmits at 17 dBm into a cable with 3 dB of loss that feeds a 9 dBi antenna. What is the EIRP?

  1. 11 dBm
  2. 20 dBm
  3. 29 dBm
  4. 23 dBm Correct answer.

Explanation

EIRP is calculated as transmit power plus antenna gain minus cable loss: 17 dBm + 9 dBi − 3 dB = 23 dBm. Cable loss is always subtracted because it reduces power reaching the antenna.